dep: bump docker/build-push-action from 2 to 6

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 2 to 6.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@v2...v6)

---
updated-dependencies:
- dependency-name: docker/build-push-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/docker.yml

@@ -52,7 +52,7 @@ jobs:
         password: ${{ secrets.QUAY_TOKEN }}
     - name: Build and push
       id: docker_build
-      uses: docker/build-push-action@v2
+      uses: docker/build-push-action@v6
       with:
         push: true
         # tags: yoanlin/bbgo:latest